JPH0551672A - High-strength and high-conductivity copper alloy for electronic equipment excellent in bendability and stress relaxation property - Google Patents

Abstract

PURPOSE:To provide an inexpensive high-strength and high-conductivity copper alloy for electronic equipment excellent in characteristics, such as strength, electric conductivity, bendability, stress relaxation property, and solderability. CONSTITUTION:The high-strength and high-conductivity copper alloy for electronic equipment has a composition consisting of 0.01-4.0% Ti, 0.05-0.8% Cr, 0.05-0.4% Zr, 0.005-<0.05% Mg, or further containing one or >=2 kinds among 0.05-2.0% Zn and 0.01-1.0%, in total, of one or more elements among Sn, In, Mn, P, Ni, Si, and Fe, and the balance Cu with inevitable impurities and also has a structure where average crystalline grain size is regulated to 35-100mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to a semiconductor integrated circuit (I
The present invention relates to a lead frame material of C) and a copper alloy suitable for electronic equipment as a conductive spring material in various terminals, connector relays, switches and the like.

[0002]

2. Description of the Related Art Conventionally, as a lead material for semiconductor devices, a kovar (Fe-29Ni-16Co) having a low coefficient of thermal expansion and good adhesiveness and sealability with semiconductor elements and ceramics. High nickel alloys such as and 42 alloy (Fe-42Ni) have been used favorably. However, in recent years, the degree of integration of semiconductor circuits has increased and the number of ICs with high power consumption has increased, and resin has been frequently used as a sealing material, and at the same time, the adhesion between the element and the lead frame has been improved. As a result, the lead material used has also come to be a "copper alloy" with good heat dissipation.

By the way, it is generally said that the lead material of a semiconductor device is required to have the following characteristics. a) At the same time that the lead is the electrical signal transmission part,
Since it also has the function of releasing the heat generated during the aging process and during the use of the circuit to the outside, it exhibits excellent heat and electrical conductivity. B) It is a lead from the viewpoint of "protection of semiconductor elements". Mode
Adhesion with the solder is important, and therefore the lead material shows a thermal expansion coefficient close to that of the mold material.c) Good heat resistance because various heating processes are performed during packaging. D) In most cases, the lead material is punched and bent during the manufacture of the lead, so the workability of these is good, and e) it is used as a lead. At that time, the surface is generally plated with a noble metal. Therefore, the adhesion with the above-mentioned noble metal plating is good. F) The so-called "outer layer" that is exposed to the outside of the encapsulant even after packaging. -Since soldering is often applied to the "lead part", good solderability is exhibited, and the solder peeling phenomenon does not occur even after long-term use. G) Device reliability and life Corrosion resistance is good, which greatly affects It.

However, the alloys conventionally used as the lead material for semiconductor devices have advantages and disadvantages with respect to the various required characteristics described above, and it is the current situation that no alloy satisfying all of them in good balance has been found. Met.

On the other hand, for spring materials such as terminals, connectors, relays or switches, conventionally, inexpensive "brass", "phosphor bronze" having excellent spring characteristics or "white silver" having excellent spring characteristics and corrosion resistance has been used. Was applied. However, brass is inferior in strength and spring characteristics,
Also, phosphor bronze, which has excellent spring properties, contains a large amount of Sn, and nickel white silver, which has both excellent strength and spring properties, contains a large amount of Sn.
In addition to containing Ni, the raw material cost is high, and there is a problem that the hot workability deteriorates and processing restrictions are added during manufacturing. In addition, when considering application to electronic equipment members whose required performance is becoming more and more sophisticated, these materials are not always satisfactory in terms of electrical conductivity, and in terms of performance as a connector. It has been pointed out that there is a drawback that "the stress relaxation property is poor at the contact portion".

Particularly, in recent years, the workability of materials has become more and more important due to the tendency toward miniaturization and thinning of electronic devices and parts thereof, and in particular, those having better bendability (bending workability). However, for this reason, the advent of an inexpensive alloy for electronic devices, which has not only excellent conductivity but also excellent spring characteristics and bendability, has been awaited.

However, in such a situation, the "Cu-Ti alloy" or "Cu-Cr alloy" satisfies the above-mentioned required characteristics as a material for electronic devices to a considerable extent.
Several new alloys were also developed in which the third and fourth elements were added to this to further improve the properties.

However, recently, high integration of semiconductor circuits
Higher reliability is accelerating more than ever before,
Along with this, the lead frame has been made to have more pins and thinner, so that the strength level required for the lead frame material is likely to be further enhanced. Also, for example, when attention is paid to connectors, high-strength materials comparable to beryllium copper are beginning to be demanded from the viewpoint of improving their reliability and heat dissipation (that is, improving heat dissipation also requires thinning). Because it will be an effective means). Therefore, Cu
Although some new copper alloys based on -Ti system and Cu-Cr system have been developed, the copper alloys developed up to now have not fully met the above requirements.

In view of the above, the object of the present invention is not only excellent in conductivity but also having strength comparable to that of a high-strength spring material and capable of increasing the number of lead frames. It was an object of the present invention to provide an inexpensive high-conductivity copper alloy for electronic devices, which can sufficiently cope with the above-mentioned problems and which exhibits stress relaxation characteristics and bendability equivalent to or higher than those of conventional copper alloys for electronic devices.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the inventors of the present invention have found that "the alloying components contain Ti, Cr, Zr and Mg in a specific ratio strictly limited. In addition, the copper alloy whose average crystal grain size is adjusted within the range of 35 to 100 μm by selecting the conditions during solution treatment has various characteristics such as strength, conductivity, bendability, and stress relaxation property in the future. In addition to having a good balance at a high level desired for equipment, a suitable amount of Zn, Sn, In, Mn, P and
It is possible to further improve the soldering characteristics and strength characteristics by adding Si. "

The present invention has been completed on the basis of the above findings and the like. "A high-strength and high-conductivity copper alloy for electronic equipment is provided with Ti: 0.01 to 4.0% (hereinafter,% representing a component ratio is a weight). %), Cr: 0.05 to 0.8%, Zr: 0.05 to 0.4%, Mg:
Contains 0.005% or more and less than 0.05%, or further Zn: 0.05 to 2.0%, one or more of Sn, In, Mn, P and Si:
It contains one or more of 0.01-1.0% of the total amount, and the balance is
High conductivity, high strength, excellent bendability and stress relaxation characteristics, and good soldering by using a composition consisting of Cu and unavoidable impurities and adjusting the average crystal grain size to 35 to 100 μm. It has a great feature in that it has both sex and the like. "

The reason why the component composition and crystal grain size of the alloy of the present invention are numerically limited as described above will be described in detail together with its action.

[Action]

A) Component ratio Ti Ti has the effect of causing a spinodal decomposition when the alloy is aged to create a concentration-modulated structure in the base material, which ensures very high strength. Amount 0.01
If less than 4.0%, the desired effect due to the above action cannot be expected, while if more than 4.0% of Ti is contained, precipitation of grain boundary reaction type is likely to occur, conversely leading to strength reduction and deterioration of workability. Therefore, the Ti content was set to 0.01 to 4.0%.

Cr Cr acts not only to precipitate in the base metal when the alloy is aged, but also to precipitate a compound that causes the above spinodal decomposition together with Ti to improve the strength and heat resistance of the alloy. However, if the content is less than 0.05%, the desired effect due to the above action cannot be expected, while if it exceeds 0.8%, the Cr content exceeds
If Cr is contained, undissolved Cr remains in the base metal even after solution treatment, and the conductivity and workability are significantly reduced. Therefore, the Cr content was set to 0.05 to 0.8%.

Zr Zr has a function of forming a compound with Cu by the aging treatment and precipitating it in the base material to strengthen it, but its content is 0.05
If it is less than%, the desired effect due to the above action cannot be obtained.
If Zr is contained in excess of 0.4%, undissolved Zr will remain in the base material even after solution treatment, resulting in a significant decrease in conductivity and workability. 0.4
Defined as%.

Mg Mg has the effect of remarkably improving the stress relaxation characteristics even when added in a trace amount, but if the content is less than 0.005%, the desired effect due to the above effect cannot be expected,
On the other hand, if the content of 0.05% or more is not only saturated but also the electrical conductivity is deteriorated, the Mg content is defined as 0.005% or more and less than 0.05%.

Zn Zn is a component added as necessary because it has a function of improving the peeling resistance of solder, but its content is 0.05
If it is less than%, the desired effect due to the above action cannot be obtained.
If the Zn content exceeds 2.0%, the electrical conductivity and stress relaxation characteristics deteriorate, so the Zn content is 0.05-2.0%.
I decided.

Sn, In, Mn, P and Si All of these components have the effect of improving the strength mainly by solid solution strengthening without greatly reducing the conductivity of the alloy, and therefore, if necessary, one kind may be used. Or, two or more kinds are added, but if the total content is less than 0.01%, the desired effect due to the above action cannot be obtained, while the total amount is 1.0%.
When the content exceeds%, the conductivity and workability of the alloy are significantly deteriorated. Therefore, the total content of Sn, In, Mn, P and Si, which is added singly or in combination of two or more, is set to 0.01 to 1.0%.

B) Grain size (average grain size) The reason why the alloy structure is limited to those having an average grain size of 35 to 100 μm is in consideration of bendability and stress relaxation characteristics. Generally, the smaller the crystal grain size is, the more preferable from the viewpoint of bendability, while the larger crystal grain size is preferable from the viewpoint of stress relaxation characteristics. However, in the copper alloy having the component composition according to the present invention, when the crystal grain size is adjusted within the range of 35 to 100 μm in terms of average crystal grain size, excellent bendability and excellent stress relaxation property are simultaneously exhibited. Become. That is, if the average crystal grain size is less than 35 μm, the bendability is further improved, but stress relaxation is likely to occur. If the average crystal grain size exceeds 100 μm, on the contrary, stress relaxation is difficult but the bendability deteriorates. Both are inferior in characteristics for electronic devices.

The grain size of the alloy is preferably adjusted during the solution heat treatment, and an appropriate grain size can be achieved by adjusting the treatment temperature, treatment time and the like.

Next, the effects of the present invention will be described more specifically by way of examples.

EXAMPLES First, electrolytic copper or oxygen-free copper was used as a raw material, and copper alloy ingots (thickness 30 mm) having various component compositions shown in Table 1 were melted in an inert atmosphere in a high frequency melting furnace. next,
Each of these ingots was successively subjected to hot rolling, solution treatment and cold rolling, and then subjected to an aging treatment at 400 ° C. and then subjected to cold rolling and strain relief annealing again to obtain a plate material.

[0021]

[Table 1]

Then, various test pieces were sampled from the obtained plate material and a material test was conducted to evaluate the characteristics as a "lead frame material" and a "spring material". The characteristics of "lead frame material" and "spring material" are "strength",
It was evaluated by investigating "elongation", "conductivity (heat dissipation)", "spring property", "solder heat-resistant peeling property", "bendability" and "stress relaxation property".

The "strength" and "elongation" were measured by a tensile test, and the "conductivity" was determined by measuring the conductivity (% IACS). Regarding the "springiness", the spring limit value (K
b) was measured.

The investigation of "solder heat resistance peeling resistance" was conducted with a material of 5μ
After applying m-thick solder (90% Sn-10% Pb) plating, 150 ℃
It was held in the high temperature tank up to 1000 hours, taken out every 100 hours during this time, and subjected to 90 ° bending reciprocation once to examine the start time of solder peeling. In addition, in the case of no peeling up to 1000 hours, the investigation result was displayed as "1000 hr".

The "bendability" was evaluated by conducting a bending process using a W bending tester and visually observing the bent portion to examine the "degree of skin roughening" and "presence of cracks". The evaluation results are indicated by ○: no rough skin and cracks occurred, ×: rough skin or cracks occurred.

Regarding the "stress relaxation characteristics", the strip-shaped test piece was once fixed and a stress was applied to the other end to apply a bending stress, and this state was maintained at 150 ° for 1000 hours, and then the stress was released. The residual strain was measured.
The results of these investigations are shown in Table 2.

[0027]

[Table 2]

From the results shown in Table 2, the following is clear. That is, the alloys 1 to 18 of the present invention are all excellent in strength, conductivity, bendability, and stress relaxation characteristics, and sufficiently good evaluations of other characteristics can be obtained.

On the other hand, the comparative alloy 19 is inferior in strength because the Zr content is not sufficient, and the comparative alloy 21 has a Ti content, and the comparative alloy 24 has a Zn content and an Mg content, respectively. Since it exceeds the value, the electrical conductivity is poor. Further, since the comparative alloy 25 does not have sufficient Ti content and Cr content and the Zr content and the Mg content exceed the respective upper limit values, the strength and the conductivity are remarkably inferior.

The comparative alloys 22, 23 and 24 have a crystal grain size (average crystal grain size) smaller than the lower limit value. Therefore, although the bendability is good, the stress relaxation characteristics are inferior. On the contrary, the comparative alloys 19, 20, 21 and 26 show the result that the bendability is poor because the grain size is larger than the upper limit value.

[0031]

[Summary of Effects] As described above, according to the present invention, strength, conductivity, bendability, stress relaxation characteristics, etc. are all excellent, and it is used for electronic equipment members such as lead frame materials and spring materials. It is possible to realize a suitable high-strength and high-conductivity copper alloy, and it is possible to make a great contribution to the performance improvement of electronic devices.

Claims (4)

[Claims] 1. By weight ratio, Ti: 0.01 to 4.0%, Cr: 0.05 to 0.8%, Zr: 0.
05-0.4%, Mg: 0.005% or more and less than 0.05%, the balance is composed of Cu and unavoidable impurities, and the average crystal grain size is adjusted to 35-100 μm. High-strength and high-conductivity copper alloy for electronic devices with excellent properties and stress relaxation characteristics. 2. Ti: 0.01 to 4.0%, Cr: 0.05 to 0.8%, Zr: 0.
05 to 0.4%, Mg: 0.005% to less than 0.05%, Zn: 0.
An electron having excellent bendability and stress relaxation characteristics, characterized by containing 05 to 2.0%, the balance being composed of Cu and unavoidable impurities, and having an average crystal grain size adjusted to 35 to 100 μm. High strength and high conductivity copper alloy for equipment. 3. Ti: 0.01 to 4.0%, Cr: 0.05 to 0.8%, and Zr: 0.
05-0.4%, Mg: 0.005% or more but less than 0.05%, and one or more of Sn, In, Mn, P and Si: 0.01-1.0% in total, with the balance Cu and unavoidable impurities. The high-strength and high-conductivity copper alloy for electronic equipment, which is excellent in bendability and stress relaxation characteristics, characterized in that the average crystal grain size is adjusted to 35 to 100 μm. 4. Ti: 0.01 to 4.0%, Cr: 0.05 to 0.8%, and Zr: 0.
05 to 0.4%, Mg: 0.005% to less than 0.05%, Zn: 0.
05 to 2.0%, and also one or more of Sn, In, Mn, P and Si: 0.01 to 1.0% in total, with the balance being Cu and inevitable impurities, and having an average grain size. Is adjusted to 35 to 100 μm, and a high-strength and high-conductivity copper alloy for electronic devices, which is excellent in bendability and stress relaxation characteristics.